A reusable liposome array and its application to assay of growth-hormone-related peptides

We describe a reusable liposome array based on the formation of cleavable disulfide cross-links between liposomes and the surface of a glass slip. The N-succinimidyl 3-(2-pyridyldithio)-propionate (SPDP)-modified liposomes encapsulating a pH-sensitive fluorescence dye were immobilized on a 3-mercaptopropyltrimethoxysilane (MTS)-modified glass slip through the formation of disulfide bonds. The regeneration of a used slip was performed by the lysis of immobilized liposomes with Triton X-100 and the cleavage of disulfide bonds by reduction with TCEP, followed by immobilization of SPDP-modified liposomes. The regeneration steps did not affect the fluorescence intensity of re-immobilized liposomes. The liposome array was applied to simultaneous quantification of growth hormone related peptides, i.e., GHRF and somatostatin, in a mixture. After optimizing the assay condition, the method allowed quantification of GHRF and somatostatin in concentration ranges from 0.5 x 10(-9) to 0.5 x 10(-7) g/mL with detection limits of 2 x 10(-10) and 3 x 10(-10) g/mL, respectively.